The present invention relates to a semiconductor device and a technique for manufacturing the same. Particularly, the present invention is concerned with a technique applicable effectively to the manufacture of a semiconductor device and including an electrical characteristics testing process for a semiconductor integrated circuit with use of a Kelvin contact method.
A process for manufacturing a semiconductor device such as LSI or IC broadly includes a pre-process (also called a wafer process) of forming integrated circuits on a main surface (an integrated circuit-forming surface) of a semiconductor wafer, e.g., a single crystal silicon wafer, by combining, for example, photolithography technique, CVD technique, sputtering technique and etching technique and a post-process of dicing the semiconductor wafer with integrated circuits formed thereon into a plurality of individual semiconductor chips and thereafter sealing each semiconductor chip with a package such as, for example, a resin or ceramic package.
In the above manufacturing process, an electrical characteristics test called a probing test is conducted in the final step of the manufacturing process. According to the probing test, metallic search units called probes are brought into contact with surfaces of a large number of electrode pads (also called bonding pads) formed on the main surface of the semiconductor wafer to test whether constituent elements of the integrated circuits are good or bad and also check whether wiring lines which couple between the elements are in conduction or not. In the post-process there is performed an electrical characteristics test called a burn-in test. In the burn-in test, a package is inserted into a dedicated testing socket and thermal and electrical stresses are applied to the semiconductor chip within the package while contacting probes with external coupling terminals (e.g., lead terminals and solder balls) of the package to do an accelerated test of a defect of the integrated circuit.
A testing apparatus used in the above electrical characteristics test has a sample support system including a probe card, a frog ring and a wafer stage for resting thereon the semiconductor wafer as an object to be tested. The probe card is comprised of the foregoing probes and a wiring substrate serving also as a support board for the probes. A typical probe is a cantilever type tungsten (W) probe extending in an oblique direction from a lower surface of the probe card. A probe called a POGO pin or a spring probe is of a configuration wherein a contact pin is pushed against an electrode pad surface under the resilience of a coil spring. For example, it is of a structure wherein a coil spring accommodated within a metallic tube (a holding member) transmits its resilience to a contact pin through a metallic ball. When performing an electrical characteristics test with use of the above testing apparatus, if a natural oxide film is formed or a contaminant is deposited on the electrode pad surface, it is impossible to carry out an exact measurement. Therefore, when contacting a probe with the electrode pad surface, there is performed a wiping operation which involves causing the probe to slide to break the natural oxide film, thereby allowing a clean metal surface to be exposed.
In the above electrical characteristics test, for measuring, for example, a circuit resistance value (impedance), there is adopted a two-terminal measuring method wherein probes are brought into contact with both-side terminals respectively of a circuit to be tested and a voltage drop is measured upon flowing of an electric current through the circuit. In the two-terminal measuring method, however, when the impedance of the circuit to be tested is low, there occurs an error which is caused by a contact resistance between terminal and probe or a line resistance of the tester. Therefore, in the case where the impedance of the circuit to be tested is low, there is adopted, instead of the two-terminal method, a measuring method called a Kelvin contact method (or a four-terminal measuring method).
FIG. 24A is an equivalent circuit diagram of a tester, explaining the principles of the Kelvin contact method, and FIG. 24B is an equivalent circuit diagram of a tester, explaining the principles of the two-terminal measuring method.
In the case of measuring an impedance (Z) of the to-be-tested circuit in terms of a voltage drop (Vz)) upon flowing of an electric current (I) in the circuit, the two-terminal measuring method measures a voltage drop (VM) by contacting probes with both-side terminals respectively of the circuit to be tested. According to this measuring method, however, voltage drops (Vrc1, Vrc2) caused by a contact resistance between terminal and probe and a tester line resistance are added in addition to the voltage drop (Vz)) caused by the impedance (Z) of the circuit to be tested, (VM=Vz+Vrc1+Vrc2). Consequently, when the impedance (Z) of the circuit to be tested is low, a measurement error caused by the contact resistance or the wiring resistance becomes large and it is impossible to obtain a highly accurate measured value.
On the other hand, in the Kelvin contact method, there are used separated lines, namely a line (force line) for passing an electric current (I) through the circuit to be tested and a line (sense line) for measuring the voltage drop (Vz) of the circuit, and two probes (a probe coupled to the force line and a probe coupled to the sense line) are brought into contact with each of both-side terminals in the circuit to measure the voltage drop (VM). According to this measuring method, no electric current flows (i=0) in the sense line coupled to a voltmeter, so that the voltage drops caused by the foregoing contact resistance and line resistance are cancelled and it is possible to measure only the voltage drop (Vz)) caused by the impedance (Z) of the circuit to be tested, (VM=Vz).
For the above reasons the Kelvin contact method is an effective and essential method for measuring at a low resistance such products of large electric current values as, for example, motor driver products, power MOS products and regulator products.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2007-285970) discloses a pin structure in a Kelvin contact measuring apparatus wherein a force pin (a force-side probe) and a sense pin (a sense-side probe) are brought into contact with an external coupling terminal (solder ball) in a semiconductor package such as BGA (Ball Grid Array) or CSP (Chip Size Package) to measure electrical characteristics.
The above force pin and sense pin are each configured so as to be capable of expansion and contraction and be urged toward the solder ball by means of a resilient member. A total number of force and sense pins for one solder ball is three or more. Both pins are disposed so as to each come one or more into contact with one solder ball. The semiconductor package is positioned so as to be capable of entering and leaving a recess of a lower socket of the measuring apparatus and the force and sense pins are supported flexibly by an upper socket frame.
Patent Document 2 (Japanese Unexamined Patent Publication No. 2008-249466) and Patent Document 3 (Japanese Unexamined Patent Publication No. 2008-249467) disclose a spiral contactor used in Kelvin contact measurement. This Kelvin contact type contactor includes a pair of contactors each having a convex spiral shape, one spiral contactor fitted in a spiral gap of the other spiral contactor. The pair of contactors are coated at least on respective side faces with an electrical insulator except contact portions for contact with terminals of an object to be tested (Patent Document 2), or are formed integrally in a state in which an electrical insulator is filled in a spiral gap (Patent Document 3). With this structure, even if fine dust gets in the groove formed between the pair of contactors, the contactors do not short with each other.
Patent Document 4 (Japanese Unexamined Patent Publication No. 2008-292337) discloses a method for testing electrical characteristics of a semiconductor device having solder balls which method permits positive wiping operation and Kelvin contact. In this testing method, cantilever type contactors are used two in a pair, the contactors each having a planar tip with a peripheral edge, a sectional diameter of the tip portion being larger than the radius of a spherical external electrode, and the contactors being supported by a support board each at a predetermined position. When the support board or the semiconductor device is pressed, the edge of each of the paired contactors comes into contact with a solder ball surface and thus Kelvin contact is made. Further, when the support board or the semiconductor device is overdriven, the edge of each contactor slides on the solder ball surface to effect wiping.